Filter apparatus

ABSTRACT

A filter device for cleaning particulate contaminants from a fluid flow, includes a plurality of filter elements ( 34, 60 ) accommodated in filter chambers ( 12, 14, 32 ) as components of a joint filter housing ( 10 ) and grouped around a backwash device ( 20 ) having a piston accumulator ( 56 ) for receiving a backwash fluid. In the storage housing ( 64 ) of the piston accumulator, a piston ( 57 ) is guided in a longitudinally movable manner, is controlled by a pressure medium, and passes on the backwash fluid stored in the storage housing ( 64 ) on to at least one filter element ( 60 ) to be backwashed for cleaning purposes via a backwash device ( 20 ). The backwash device also discharges the backwash fluid from the filter device. A specific filter element as a bypass filter element ( 34 ) is selected from the plurality of filter elements ( 34, 60 ), and exclusively removes particles after a changeover device ( 18 ) has been actuated, while the other filter elements ( 60 ) are excluded from this removal process.

FIELD OF THE INVENTION

The invention relates to a filter device for cleaning particulatecontaminants from a fluid flow. A plurality of filter elements areaccommodated in filter chambers as components of a joint filter housingand are grouped around a backwash device having a piston accumulator forreceiving a backwash fluid. In the storage housing of the pistonaccumulator, a piston is guided in a longitudinally movable manner, iscontrolled by a pressure medium and passes the backwash fluid stored inthe storage housing on to at least one filter element to be backwashedfor cleaning purposes via a backwash device. The backwash device alsodischarges the backwash fluid from the filter device.

BACKGROUND OF THE INVENTION

Such a filter device is known from WO 2012/150011 A1, for instance. Theknown filter device comprises a pressure control device to support thebackwashing of individual filter elements having a hydraulicaccumulator. One fluid chamber of the hydraulic accumulator can befilled with a quantity of cleaned fluid during the filtration processand can for a backwashing process be connected to the clean side of thefilter element to be cleaned via a backwash duct. A further fluidchamber of the hydraulic accumulator can be pressurized by a gaspressure for a backwash process to at least partially discharge thefilling quantity of the cleaned fluid for the backwash process of afilter element from the one fluid chamber by a movement of theseparating element of the hydraulic accumulator caused by the gaspressure.

Such filter devices are also regularly used in marine applications, inparticular in marine engines. The International Maritime Organization(IMO) has tightened the limit values for climate-relevant exhaust gasesfrom ships, such as nitrogen oxides and sulfur oxides, as part of theTier III standard, which has come into force in 2016. The manufacturersof modern marine engines are therefore increasingly relying oncommon-rail systems to reduce fuel consumption and exhaust gases. Thisreliance results in new requirements for the efficient fluid managementof marine engines and the resulting increased demands on the purity offuels and lubricants on board of ships.

Such filter devices are regularly provided with bypass filters, throughwhich the fluid flow to be cleaned, regularly being heavy fuel oil,diesel, biofuels and lubricating oil, is routed exclusively for cleaningpurposes, as soon as the bypass filter, controlled by a changeoverdevice, permits the actual filter device to be shut down for maintenanceand inspection purposes, including replacing used filter elements withnew elements in this context.

Experience has shown that the solutions described above are large and,from a design engineering point of view, on-site installation is oftencomplex and therefore costly. In addition, the different installationlocations of filter devices and assigned bypass filters, even if theyare arranged adjacent to each other, result in different thermaloperating situations. Those situations can have unfavorable effects onfluid treatment, particularly in relation to fluid filtration.

Furthermore, a principal objective is to be able to use the provenfiltration technology in the context of fuel supply for marine enginesand their lubrication for other new areas of application, for instancein the context of filtering cooling lubricants in machine tools, etc.

SUMMARY OF THE INVENTION

Based on this state of the art, the invention addresses the problem offurther improving the known filter devices, while maintaining theadvantages of the known filter devices, i.e., to ensure a safefiltration of particle contamination from fluids, such that new fieldsof application for this filtration technology can be developed and suchthat installation space when setting up can be reduced and costs can bereduced, with improved thermal conditions during the operation of suchdevices. A filter device according to the invention solves this problem.

Because by selecting a specific filter element as a bypass filterelement from the plurality of filter elements of the device, thisspecific filter element exclusively removes particles after a changeoverdevice has been actuated and the other filter elements are excluded fromthis removal process. The bypass filter element or the bypass filteritself is an integral part of the overall filter housing in conjunctionwith the other filter elements of the device. The filter elements eachhave an independent filter chamber, which form the filter housing as awhole. In the practical implementation of the invention by integratingthe bypass filter element into the overall system of filter elements inonly one housing device, in particular if the filter housing is made ofcast steel, a uniform thermal heat distribution within the filter devicehaving the bypass device is achieved. The previously existing danger ofthermally induced stress cracks in the housing has been effectivelyeliminated, there is a homogenized thermal entry of the hot or at leastwarm (at operating temperature) fluid into the housing including itsindividual components, such as the filter element and the backwashdevice, during operation of the device, resulting in a positive effecton fluid filtration.

In this respect, the filter device according to the invention also has acompact design and can therefore be installed in places offering limitedinstallation space, as is the case for coolant filtration of machinetools. Because solely one filter housing having filter chambers for allfilter elements including the bypass filter element has to be provided,preferably within the framework of a single steel casting, the filterdevice according to the invention is also cheap to manufacture. Becauseof the central arrangement of all components in and on the centralhousing, the installation and maintenance costs are also reduced.

In an advantageous design, the bypass filter integrated in the filterhousing and its filter element can also be used for starting up fuelsystems and other hydraulic systems of any kind, in which very high dirtloads of particle contamination can occur by initially excluding thefurther filter device with its filter elements from the filtrationprocess. If the individual bypass filter element can no longer be useddue to the ingress of dirt, it may be replaced by a new element. Thereplacement may be performed several times until a normal operatingsituation is established, in which case the system is switched to normalfiltration mode in addition to backwashing using the further filterdevice, bypassing the bypass filter.

In another advantageous design, provision can be made to select thearrangement of the bypass filter element and the other filter elementsof the filter device such that all filter elements can be cleaned insuccession using only one backwash device. In this way it would bepossible to use the bypass filter element as a further filter elementfor filtration purposes as well, like the other filter elements of thefilter device in addition to its bypass filtration function.

In a preferred embodiment of the filter device according to theinvention, the changeover device is also accommodated in the jointfilter housing and has a distribution device which, in its one switchposition bypassing the bypass filter element, supplies the other filterelements, insofar as they are not subject to backwashing, withunfiltered medium and discharges the filtrate and which, in a furtherswitch position bypassing these filter elements, supplies the bypassfilter element with unfiltered medium and discharges the filtrate. Thedistribution device provides the proper branching and allocation of thefluid paths in the filter device. In start-up mode, the fluid flowcontaining coarse contamination is routed to the bypass filter elementas unfiltered medium and is cleaned there using a suitable filtermaterial having preferably a lower grade of filtration. The other filterelements are then excluded from the filtration mode.

During regular mode of the filter device, the uncleaned or contaminatedfluid flow is routed to the other filter elements as unfiltered mediumflow and cleaned using a suitable, predeterminable filter material. Thebypass filter element then is excluded from the filtration mode.However, in principle it would also be possible to integrate the bypassfilter element into the regular filtration mode after completingstart-up mode and the assigned cleaning by the backwash device. Due tothe compact arrangement of the components of the filter device accordingto the invention in a joint filter housing, preferably made of caststeel, the filter elements used in regular mode are uniformly subjectedto fluid, even at accordingly high operating temperatures, e.g. 130° C.,preventing harmful thermal stresses in the filter housing.

Preferably, the changeover device is arranged adjacent to the bypassfilter element and can be operated manually or mechanically by anoperator. It is also advantageous to form the changeover device as achangeover fitting that can be moved manually between the switchpositions by a hand lever. The hand lever, which is particularlypreferably designed as a single-arm lever, is located at a point of thefilter housing easily accessible for an operator, preferably on the top.In addition to ease of use and a simple design, the hand lever offersthe advantage that the individual switch position of the changeovervalve is indicated by the position of the hand lever and can be checkedby an operator without additional effort. To increase operational safetyand for remote maintenance purposes, at least one sensor for monitoringthe switch position of the changeover device can be provided on thefilter device in accordance with the invention.

In a further preferred embodiment of the invention, at least one filterelement from the plurality of filter elements, including the bypassfilter element, can be backwashed by the backwash device. The filterelements arranged in individual filter chambers are typically backwashedin succession and in continuous sequence and freed from dirt particlesadhering to the relevant filter material in the return flow. By thecontinuous and demand-oriented backwashing of the individual filterelements, the high purity requirements of fuels and lubricants is takeninto account. By the attendant dirt discharge, a high performance of thefilter device is ensured.

To backwash a filter element, the backwash device, which is preferablyrotatable around the symmetry axis of the filter housing, is rotatedtowards the filter element to be backwashed. The backwash fluidpressurized by the pressure medium is fed to the filter element to becleaned through a backwash channel and discharged from the filter devicevia a further backwash channel and a backwash line connected thereto.The backwash channels are part of the backwash device and are preferablyarranged rotatably in the filter housing via a joint drive. Depending onthe arrangement and flow direction of the filter elements duringfiltration mode, from the inside to the outside or from the outside tothe inside, the position of the individual backwash channel is selectedin relation to the filter element, above, below or lateral thereof. Aparticularly compact design of the filter device according to theinvention is achieved by a cylindrical backwash device that is rotatablyarranged in a main part of the filter housing and whose backwashchannels are arranged in the individual backwash positions at fluidsupply ducts and fluid discharge ducts to and from the filter chambersbranching off laterally from the main part.

In a further preferred embodiment of the filter device according to theinvention, the changeover device has a spindle, which can be rotated ina spindle housing as part of the filter housing and which has two fluidchannels separated from each other on the outer circumference andconnected to a fluid inlet of the filter housing for the supply ofunfiltered medium and to a fluid outlet for discharging filtrate. In oneswitch position of the changeover device, the two fluid channels areconnected to the filter elements provided for filtration and to thebypass filter element in the other switch position. The fluid channels,which preferably extend horizontally and vertically on the outside ofthe spindle, ensure besides short fluid paths a good heat transfer fromthe fluid flow guided in the fluid channels to the wall parts of thefilter housing encompassing the spindle. The specifications “horizontal”and “vertical” refer to the usual installation or mounting position ofthe filter device according to the invention, whose filter elements andfilter chambers generally run in the vertical installation direction.

The spindle being rotatably arranged in a part of the filter housingresults in a compact, space-saving structure of the changeover device.Typically, the spindle housing has an installation size comparable tothat of a filter chamber. Advantageously, the fluid inlet and the fluidoutlet are arranged on an outer wall part of the filter housingencompassing the spindle housing. The fluid inlet and fluid outlet arepreferably arranged vertically one above the other to save installationspace.

In a further preferred embodiment of the filter device according to theinvention, two fluid ducts separated from each other are provided on aninner wall of the filter housing, relative to the position of the pistonaccumulator, within the filter housing. These fluid ducts at leastpartially encompass the piston accumulator and, in one switch positionof the changeover device, are connected in a fluid-conveying manner tothe assignable fluid channels in such a way that filtration is madepossible using the filter element provided for this purpose in eachcase. The filter element is flowed through from the outside to theinside for removing particles. A defined fluid routing of the fluid tobe cleaned is ensured in a functionally reliable manner according to theindividual switch position of the changeover device by the fluidchannels and fluid ducts formed in the filter housing.

In a further preferred embodiment of the filter device according to theinvention, the backwash device cleans the particle contamination incounterflow to the direction of filtration from the filter elementprovided for this purpose. Two backwashing channels are arrangedopposite from each other and are guided in the filter housing in afluid-conveying manner with the two opposite ends of the filter elementto be backwashed, thereby shutting off the two fluid ducts for thefiltration process. Of the two backwash channels, one supplies thepressurized backwash fluid preferably from above, and the otherdischarges the contaminated backwash fluid preferably from below. Thetwo backwash channels are rotatable via preferably a joint drive and canbe positioned as required at the fluid discharge duct and the fluidsupply duct of the filter element to be cleaned. The duration and thefrequency of a backwashing process at the individual filter element canbe selected according to individual requirements or automaticallyadjusted according to a predetermined cleaning cycle. If a certaindegree of contamination of the filter materials of the filter elementsis detected, for instance if a pre-settable differential pressure isexceeded, the backwashing process can be started, and the filterelements can be cleaned in succession by the backwash device.

A particularly compact and stable structure of the filter deviceaccording to the invention is achieved by closing the lower bottom endsof the respective filter elements and having a fluid discharge duct attheir upper end. The upper end is closed off from the assignable filterchamber, which encloses the individual filter element at a radialdistance. When the filter elements closed at one end are arranged in theindividual filter chamber, the fluid path for cleaning the fluid flow isdefined in that the unfiltered medium flows into the individual filterchamber from a radial side via the fluid ducts formed in the filterhousing and flows from the outside to the inside through the filterelement arranged therein. When flowing through the filter element fromthe outside to the inside, the particulate contaminants remain on theoutside of the filter material of the relevant filter element, and thefiltrate is returned to the fluid discharge duct via the fluid dischargeat the upper end of the filter element.

In another preferred embodiment of the invention, the piston accumulatorhas a filtrate space above its piston for receiving filtrate from thefilter device and has a control space below the piston for receivingcompressed gas. The compressed gas moves the piston upwards therebydisplacing the filtrate in the filtrate space, which cleans the filterelement from particle contamination from the inside to the outside viathe upper backwash channel and the fluid discharge duct in the filterelement. At least a part of the fluid cleaned off at the individualfilter elements can be accommodated in the filtrate space and is used asa washing liquid for cleaning a filter element to be cleaned, whilepressurizing the piston using compressed gas as a pressure medium.Preferably, the entire volume of the filtrate taken up in the filtratespace is used as a backwash fluid during a backwash process and is fedinto the filter cavity of the filter element via the correspondingbackwash channel. The corresponding filter element is cleaned from theinside to the outside, opposite to the direction of filtration. Thepressure surge when moving the piston in the piston accumulator resultsin a pulse-like cleaning of the filter material.

A further advantage is that the lower backwash channel of the backwashdevice, connected to the filter chamber of the filter element to bebackwashed, is used to remove the particle contamination from the filterdevice. This arrangement makes for a compact, reliable design of thebackwashing laterally parallel to the regular filtration mode.

The above-mentioned features and the further cited features according tothe invention can be implemented individually or in any combination in afilter device according to the invention and for the designated use.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the drawings, discloses a preferred embodimentof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings that form a part of this disclosure and thatare schematic and not to scale:

FIG. 1 is a perspective view of a filter device according to anexemplary embodiment of the invention;

FIG. 2 is a top plan view of the filter device of FIG. 1;

FIG. 3 is a perspective view partially in section of the filter deviceof FIG. 1 illustrating the bypass mode;

FIG. 4 is a perspective view partially in section of the filter deviceof FIG. 1 illustrating the filtration mode; and

FIG. 5 is a perspective view partially in section of the filter deviceof FIG. 1 illustrating the backwash mode.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an overall view of the filter device according to anexemplary embodiment of the invention having a filter housing 10, whichhas three filter chambers, a first filter chamber 12, a second filterchamber 14 and a third filter chamber 32 (see FIG. 2), a spindle housing24, a main housing part 16 and a drive unit 22. A fluid inlet 28 isprovided on the spindle housing 24 for the supply of fluids to becleaned. An outlet 30 is provided for discharging cleaned fluids. Afilter element 34 (see FIG. 3), 60 (see FIG. 4) is inserted in eachfilter chamber 12, 14, 32. A central component of the filter device is achangeover device or switch 18, which is enclosed by the spindle housing24 and of which only an actuating device in form of a hand lever 26 isvisible in FIG. 1. Further, a backwash device or backwasher 20 isprovided on the filter device, which backwash device is accommodated inthe main housing part 16 and of which the drive unit 22 arranged abovethe main housing part 16 is visible in FIG. 1.

In the at least partly sectional illustrations of FIGS. 3, 4 and 5, thebypass mode is illustrated in FIG. 3, the filtration mode is illustratedin FIG. 4, and the backwash mode is illustrated in FIG. 5. The top viewof the filter device of FIG. 2 shows the filter chambers 12, 14, 32 andthe spindle housing 24 arranged on a circular line such that theyconcentrically encompass a hydraulic accumulator located therebetween inthe main housing part 16. As FIGS. 4 and 5 show, a piston accumulator 56forms the hydraulic accumulator.

FIG. 3 illustrates bypass mode, in which fluid flowing into the filterhousing 10 at the fluid inlet 28 is purified at the bypass filterelement 34 in the first filter chamber 12 and routed to the fluid outlet30 as filtrate. The changeover device 18 formed as a changeover fittingcan be shifted manually between the switch positions by the hand lever26 and has a spindle 25 rotatably arranged in the spindle housing 24. Inthe switch position of the changeover device 18 shown in FIG. 3, thefluid channels 36, 38 formed on the spindle 25 are connected to thefirst filter chamber 12 in a fluid-conveying manner. In the first filterchamber 12, the cylindrical bypass filter element 34 is arranged in aholder 42 and has a closed bottom 40.

The unfiltered medium passes from the fluid inlet 28 to an inlet space46 of the first filter chamber 12 via the first fluid channel 36extending horizontally and formed in the spindle 25 and a firstconnecting piece 37 formed in the spindle housing 24. The inlet space 46radially encompasses the bypass filter element 34. In the exemplaryembodiment shown, the bottom 40 of the bypass filter element 34 isspaced apart from the bottom of the first filter chamber 12, so that thepart of the interior space of the first filter chamber 12 located belowthe bottom 40 also has to be assigned to the inlet space 46. Theunfiltered medium flows from the inlet space 46 through the bypassfilter element 34, is cleaned there and reaches a filter cavity 48. Fromthe filter cavity 48 the filtrate reaches a fluid discharge duct 44located above the holder 42 and further on the fluid outlet 30 via asecond connector 39 formed in the spindle housing 24 and via the secondfluid channel 38 formed in the spindle 25.

The first and second connecting pieces 37, 39 each have a channel widthcomparable to the fluid channels 36, 38 and differ in their fluid pathsin that the first connecting piece 37 starting from the first fluidchannel 36 drops at a step-shaped gradient towards the inlet space 46,and in that the second connecting piece 39 starting from the fluiddischarge duct 44 drops at a step-shaped gradient towards the secondfluid channel 38. The fluid routing shown in FIG. 3 is possible becausethe spindle housing 24 is arranged immediately adjacent to the firstfilter chamber 12 and is preferably formed integral therewith. Thisside-by-side arrangement is clearly visible in the plan view of FIG. 2.FIG. 2 further shows that the second and third filter chambers 14, 32and the spindle housing 24 are arranged equidistantly from each other onthe main housing part 16 in relation to the axis of symmetry R (seeFIG. 1) of the main housing part 16. The axis of symmetry R of the mainhousing part 16 is also the axis of rotation of an output shaft of thedrive unit 22, for instance in the form of an electric motor.

The bypass filter element 34 and the filter element 60 arranged in thethird filter chamber 32 (cf. FIG. 5) are each of hollow cylindrical inshape. A conically tapering shape is also feasible as an alternative tothe cylindrical shape. The filter elements 34, 36 can be formed asfilter cartridges. A metal fiber fleece, a dutch weave or a square meshfabric is preferably used as the filter material. The filter element 60used to remove the particulate contamination occurring during a regularmode preferably has a filter material having a higher grade offiltration than that of the bypass filter element 34.

In filtration mode of the filter device shown in FIG. 4, the switchposition of the changeover device 18 is selected such that, bypassingthe bypass filter element 34, the other filter elements 60, providedthey are not subject to backwashing, are supplied with unfiltered mediumand the filtrate is discharged. In doing so, the hand lever 26, which isfirmly connected to the spindle 25, is swiveled clockwise by approx.120° in plan view in relation to the bypass position shown in FIG. 2.

In the functional position of the filter device shown in FIG. 4,unfiltered medium flowing into the filter housing 10 at the fluid inlet28 reaches a chamber 53 in the bottom of the main housing part 16 viathe first fluid channel 36 and the first connecting piece 37 and afurther inlet space 59 of the third filter chamber 32 via a firstfurther connecting piece 58. A filter element 60 is arranged in thethird filter chamber 32 comparable to the arrangement of the bypassfilter element 34 in the first filter chamber 12 (see FIG. 3). The fluidflows in the radial direction from the further inlet space 49 throughthe filter element 60 and reaches a further fluid discharge duct 62 viaa further filter cavity 61. The filtrate flows from the further fluiddischarge duct 62 to a chamber 55 on the cover side in the main housingpart 16 via a second further connecting piece 63 and to the fluid outlet30 via the second connecting piece 39 and the second fluid channel 38.

A piston accumulator 56 is arranged coaxially to the axis of symmetry Rin the main housing part 16, on the housing 64. In the pistonaccumulator 56, the bottom-side chamber 53 and the cover-side chamber 55are separated from each other by a partition wall 65. On an inner wallof the filter housing 10, there are two fluid ducts 52, 54 that areseparated from each other in relation to the position of the pistonaccumulator 56. Fluid ducts 52, 54 at least partially encompass thepiston accumulator 56 and are connected to the respective assignablefluid channels 36, 38 in the switch position of the changeover device 18shown in FIG. 4.

The filter element 60 arranged in the third filter chamber 32 isbackwashed in the functional position of the filter device shown in FIG.5. The backwash device 20 comprises two washing arms 68, 70 formed onthe piston accumulator 56, which washing arms are guided to the assignedfilter chambers 12, 14, 32 by an assigned rotary movement of the pistonaccumulator 56. The washing arms 68, 70 block the two fluid ducts 52, 54for a filtration process in the third filter chamber 32. In this way,fluid can be filtered using one filter element and the other filterelement can be simultaneously backwashed. The interior space of thepiston accumulator 56 is subdivided by a piston 57, which can be movedlongitudinally in the storage housing 64, into a filtrate space 67 forreceiving filtrate from the filter device and a control space 56 forreceiving compressed gas. Filtrate flows from the chamber 55 on thecover end into the filtrate space 67 of the piston accumulator 56 via afilling bore 50, which is formed in the wall of the upper washing arm 68and which is preferably stepped in diameter to form a narrow inletopening, and fills this filtrate space 67, while the piston 57 of thepiston accumulator 56 moves downwards into the position shown in FIG. 5.

The gas is stored in a gas tank 66, which is located adjacent to thesecond and third filter chambers 14, 32 on the filter housing 10, seeFIG. 2. For backwashing, the piston 57 is driven upwards by feedingcompressed gas into the control space 61, as illustrated by the arrow72, to create a flow in the manner of a pressure surge from the filtratelocated in the filtrate space 67. The pressure surge reaches the furtherfilter cavity 61 via an upper backwash channel 69, which ispredetermined by the upper washing arm 68, the second further connectingpiece 63 and the further fluid discharge duct 62. When flowing throughthe filter element 60 from the inside to the outside, the particulatecontamination adhering to the filter material is removed and thebackwash fluid including the contaminants is discharged via the furtherinlet space 59 and a lower backwash channel 71 specified by the lowerwashing arm 70 into a valve-controlled backwash line 74, and in that wayout of the filter device.

While one embodiment has been chosen to illustrate the invention, itwill be understood by those skilled in the art that various changes andmodifications can be made therein without departing from the scope ofthe invention as defined in the claims.

The invention claimed is:
 1. A filter device for cleaning particulatecontaminants from a fluid flow, the filter device comprising: a commonfilter housing having first, second and third filter chambers withfirst, second and third filter elements in the first, second and thirdfilter chambers, respectively, having an inlet for receiving unfiltrateand having an outlet for discharging filtrate; a backwasher having thefirst, second and third filter chambers grouped about the backwasher,the backwasher including a piston accumulator housing and a pistonguided for longitudinal movement in the accumulator housing andactivated by a pressure medium, a quantity of backwash fluid beingreceivable in the accumulator housing, being selectively conveyable toat least one of the second and third filter elements to be cleaned bythe backwash fluid and being removable from one of the second and thirdfilter elements being backwashed with particle contaminants removed bythe backwash fluid; a bypass filter element formed by the first filterelement; and a switch selectively and exclusively connecting the bypassfilter element to carry out the particle cleaning of a fluid flow intothe common filter housing while the second and third filter elements areexcluded from cleaning the filter flow, the switch being accommodated inthe common filter housing, in a first position of the switch the bypassfilter element being blocked from fluid communication with the inlet andthe outlet while the second and third filter elements being in fluidcommunication with the inlet and the outlet, in a second position of theswitch the bypass filter element being in fluid communication with theinlet and the outlet while the second and third filter elements beingblocked from fluid communication with the inlet and the outlet.
 2. Afilter device for cleaning particulate contaminants from a fluid flow,the filter device comprising: a common filter housing having first,second and third filter chambers with first, second and third filterelements in the first, second and third filter chambers, respectively; abackwasher having the first, second and third filter chambers groupedabout the backwasher, the backwasher including a piston accumulatorhousing and a piston guided for longitudinal movement in the accumulatorhousing and activated by a pressure medium, a quantity of backwash fluidbeing receivable in the accumulator housing, being selectivelyconveyable to at least one of the second and third filter elements to becleaned by the backwash fluid and being removable from one of the secondand third filter elements being backwashed with particle contaminantsremoved by the backwash fluid; a bypass filter element formed by thefirst filter element; and a switch selectively and exclusivelyconnecting the bypass filter element to carry out the particle cleaningof a fluid flow into the common filter housing while the second andthird filter elements are excluded from cleaning the filter flow, theswitch being accommodated in the common filter housing and including adistributor having a first switching positon bypassing the bypass filterelement and supplying the second and third filter elements not beingbackwashed with unfiltered medium and discharging the filtrate from thesecond and third filter element not being backwashed, and having asecond switching position supplying only the bypass filter element withthe unfiltered medium and discharging filtrate from the bypass filterelement.
 3. A filter device according to claim 2 wherein the switchcomprises a switchover valve manually operable between the first andsecond switching positons by a manual lever.
 4. A filter deviceaccording to claim 1 wherein each of the first, second and third filterelements can be individually backwashed by the backwasher.
 5. A filterdevice according to claim 1 wherein the switch comprises a spindlerotatable in a spindle housing that is part of the common filterhousing, the spindle including first and second fluid channels beingseparated from each other on an outer circumference of the spindle andbeing connected to a filter inlet in the common filter housing supplyingunfiltered medium and to a fluid outlet in the common filter housingdischarging filtrate, respectively, the first and second fluid channelsbeing connected in fluid communication only to at least one of thesecond and third filter elements in a first switching position and onlyto the bypass filter element in a second switching position.
 6. A filterdevice according to claim 5 wherein an inner wall of the common filterhousing has first and second fluid ducts being separated from each otherrelative to a position of the piston accumulator, partially surroundingthe piston accumulator, and being connected to the first and secondfluid channels, respectively, in the first switching position forfiltering through the second and third filter elements from an outsidethereof to an inside thereof.
 7. A filter device according to claim 5wherein the backwasher cleans particle contaminants selectively from thesecond and third filter elements by providing a counterflow to afiltration direction via first and second backwashing channels beingarranged opposite to each other, being routed movably in the switch andbeing selectively in fluid communication with opposing ends of thesecond and third filter elements being backwashed, while the first andsecond fluid ducts are shut off.
 8. A filter device for cleaningparticulate contaminants from a fluid flow, the filter devicecomprising: a common filter housing having first, second and thirdfilter chambers with first, second and third filter elements in thefirst, second and third filter chambers, respectively, the first, secondand third filter elements being closed at bottom axial ends and havingfluid discharge openings at upper axial ends closed off relative to thefirst, second and third filter chambers and surrounding the first,second and third filter elements, respectively, with a radial gaptherebetween; a backwasher having the first, second and third filterchambers grouped about the backwasher, the backwasher including a pistonaccumulator housing and a piston guided for longitudinal movement in theaccumulator housing and activated by a pressure medium, a quantity ofbackwash fluid being receivable in the accumulator housing, beingselectively conveyable to at least one of the second and third filterelements to be cleaned by the backwash fluid and being removable fromone of the second and third filter elements being backwashed withparticle contaminants removed by the backwash fluid; a bypass filterelement formed by the first filter element; and a switch selectively andexclusively connecting the bypass filter element to carry out theparticle cleaning of a fluid flow into the common filter housing whilethe second and third filter elements are excluded from cleaning thefilter flow, the switch being accommodated in the common filter housing.9. A filter device according to claim 8 wherein the piston accumulatorcomprises a filtrate chamber above the piston receiving filtrate fromthe second and third filter elements and a control chamber below thepiston receiving compressed gas moving the piston in a upward directiondisplacing the filtrate in the filtrate chamber into the second andthird filter elements when being backwashed via an upper backwashchannel and the respective discharge opening cleaning the respectivefilter element of the particle contaminants from an inside to an outsideof the respective filter element.
 10. A filter device according to claim9 wherein the backwasher comprises a lower backwash channel beingconnected selectively in fluid communication to the second and thirdfilter chambers being backwashed and removing the particle contaminantsfrom the respective filter chamber.